Determination of Ncs parameter and logical root sequence assignments

ABSTRACT

A method for configuring a ZeroCorrelationZoneConfig (Ncs) parameter of a base station is provided. The method comprises determining a count of timing synchronization failures between a mobile device and the base station. The method comprises upon determining that the count of timing synchronization failures satisfies a threshold, dynamically configuring an Ncs parameter. The method further comprises detecting an occurrence of a timing synchronization failure. The detecting the occurrence of the timing synchronization failure comprises receiving a first message comprising a preamble, generating a preamble identification (ID) for the received preamble, transmitting a second message comprising the preamble ID, and upon transmission of the second message, detecting a non-receipt of a third message.

CLAIM OF PRIORITY UNDER 35 U.S.C. § 119

The present Application for Patent is a continuation of and claimspriority to Non-Provisional application Ser. No. 13/761,149 entitled“DETERMINATION OF NCS PARAMETER AND LOGICAL ROOT SEQUENCE ASSIGNMENTS”filed Feb. 6, 2013. Non-Provisional application Ser. No. 13/761,149, nowissued as U.S. Pat. No. 9,055,528, has been assigned to the assigneehereof and is hereby expressly incorporated by reference herein.

BACKGROUND

The following relates generally to wireless communication, and morespecifically to systems and methods to identify and optimizeZeroCorrelationZoneConfig (Ncs) parameter and logical root sequenceassignments. Wireless communications systems are widely deployed toprovide various types of communication content such as voice, video,packet data, messaging, broadcast, and so on. These systems may bemultiple-access systems capable of supporting communication withmultiple users by sharing the available system resources (e.g., time,frequency, and power). Examples of such multiple-access systems includecode-division multiple access (CDMA) systems, time-division multipleaccess (TDMA) systems, frequency-division multiple access (FDMA)systems, and orthogonal frequency-division multiple access (OFDMA)systems.

Generally, a wireless multiple-access communications system may includea number of base stations, each simultaneously supporting communicationfor multiple mobile devices. Base stations may communicate with mobiledevices on downstream and upstream links. Each base station has acoverage range, which may be referred to as the coverage area of thecell. At power-on, or after a long standby time, a mobile device may notbe synchronized with the base station. To achieve synchronization, themobile device may carry out a Random Access (RA) procedure with the basestation. In order to distinguish between different mobile devicesperforming an RA procedure, different preambles may be transmitted bydifferent mobile stations to request access to the base station.Preamble structures may have a certain level of orthogonality todistinguish between different users. Such preambles may be derived fromcyclic sequences. Different preambles may be derived from a same basesequence by introducing cyclic shifts or different preambles may bederived from different base sequences. A base station may have one ormore base sequences assigned to it along with an allowed cyclic shift.The Ncs parameter indicates the amount of cyclic shift of the rootsequence (or base sequence) to provide orthogonality between differentpreambles generated from each shift of the root sequence. Differentroots (or groups of roots) may be assigned to different base stations sothat preambles generated by devices in the coverage area of one basestation are not detected by another base station. Moreover, a minimumphysical distance should be secured before reusing the same rootsequences at another base station. The physical distance should be farenough to allow attenuation for possible users performing random accesschannel (RACH) procedures with their serving base station.

Planning the use of root sequences in networks is a non-trivial task.This planning may be assisted by implementing Self-Optimizing Network(SON) features to allow the optimum values for certain parameters to bederived based on actual measurements. The number of root sequences usedby a base station should be minimized to allow for larger reusedistance, (i.e., the distance between base stations that use the sameroot sequences may be increased). However, reducing the number of rootsequences used by a base station implies reducing the length of thecyclic shift (i.e., reducing the Ncs parameter). The length of thecyclic shift depends on the size of the cell of the base station and itcannot be reduced too much

SUMMARY

Some implementations provide a method for configuring aZeroCorrelationZoneConfig (Ncs) parameter of a base station. The methodcomprises determining a count of timing synchronization failures betweena mobile device and the base station. The method comprises, upondetermining that the count of timing synchronization failures satisfiesa threshold, dynamically configuring an Ncs parameter.

Some other implementations provide a base station for configuring aZeroCorrelationZoneConfig (Ncs) parameter. The base station comprises aprocessor and a memory in electronic communication with the processor.The memory embodies instructions. The instructions are executable by theprocessor to determine a count of timing synchronization failuresbetween a mobile device and the base station, and upon determining thatthe count of timing synchronization failures satisfy a threshold,dynamically configuring an Ncs parameter.

Yet other implementations provide an apparatus for configuring aZeroCorrelationZoneConfig (Ncs) parameter. The apparatus comprises meansfor determining a count of timing synchronization failures between amobile device and a base station. The apparatus comprises means fordynamically configuring an Ncs parameter upon determining that the countof timing synchronization failures satisfies a threshold.

Yet other implementations provide a computer program product forconfiguring a ZeroCorrelationZoneConfig (Ncs) parameter of a basestation. The computer program product comprises a non-transitorycomputer-readable medium storing instructions executable by a processorto determine a count of timing synchronization failures between a mobiledevice and the base station and upon determining that the count oftiming synchronization failures satisfies a threshold, dynamicallyconfiguring an Ncs parameter.

BRIEF DESCRIPTION OF THE DRAWINGS

A further understanding of the nature and advantages of the presentinvention may be realized by reference to the following drawings. In theappended figures, similar components or features may have the samereference label. Further, various components of the same type may bedistinguished by following the reference label by a dash and a secondlabel that distinguishes among the similar components. If only the firstreference label is used in the specification, the description isapplicable to any one of the similar components having the same firstreference label irrespective of the second reference label.

FIG. 1 shows a block diagram of a wireless communications system.

FIG. 2 is a block diagram illustrating one embodiment of an evolvedNodeB (eNB), in accordance with the present systems and methods.

FIG. 3 is a block diagram illustrating a further embodiment of an eNB,in accordance with the present systems and methods.

FIG. 4 is a block diagram illustrating an additional embodiment of aneNB, in accordance with the present systems and methods.

FIG. 5 is a message flow diagram of a connection setup procedure betweenan eNB and a user equipment (UE).

FIG. 6 is a block diagram illustrating one embodiment of a coverage areaof a cell of an eNB.

FIG. 7 is a block diagram illustrating one embodiment of a UE, inaccordance with the present systems and methods.

FIG. 8 is a block diagram illustrating a further embodiment of a UE, inaccordance with the present systems and methods.

FIG. 9 is a block diagram illustrating an additional embodiment of a UE,in accordance with the present systems and methods.

FIG. 10 is a message flow diagram of a connection setup procedurebetween a UE and an eNB.

FIG. 11 is a block diagram of a multiple-input multiple-output (MIMO)communication system including an eNB and an UE.

FIG. 12 is a flow chart illustrating one embodiment of a method foradjusting an Ncs parameter.

FIG. 13 is a flow chart illustrating one embodiment of a method formaintaining a counter of timing synchronization failures to determinewhether to adjust an Ncs parameter;

FIG. 14 is a is a flow chart illustrating one embodiment of a method foradjusting an Ncs parameter based on a number of timing synchronizationfailures that occur within a certain Ncs coverage area of an eNB.

FIG. 15 is a is a flow chart illustrating one embodiment of a method fordynamically adjusting an assignment of root sequences used to derivepreambles across a plurality of eNBs.

FIG. 16 is a flow chart illustrating one embodiment of a method formaintaining a log of timing synchronization failures to report to aneNB.

DETAILED DESCRIPTION

In Long Term Evolution (LTE) systems, Physical Random Access Channel(PRACH) preambles may be derived from a base root sequence (e.g., aZadoff-Chu sequence). To increase the number of available sequences,while keeping a certain level of orthogonality between differentpreambles derived from each base root sequences, a cyclic shift may beapplied over the base root sequence. The value of the cyclic shifts ofthe root sequences (i.e., base sequences) may be represented by aZeroCorrelationZoneConfig (Ncs) parameter. According to aspects of thepresent systems and methods, a Self-Optimized Network (SON) may allowbase stations and network configurations to be may automaticallyadjusted based on real measurements. In one configuration, the presentsystems and methods allow an SON in an LTE environment to adjust Ncsvalues based on measurements (e.g., counts) of timing synchronizationfailures that occur during a RACH process. For example, the Ncs valuemay be adjusted to an optimized value by counting the number ofincorrectly decoded PRACH preambles that are detected as originatingfrom a certain geographical region of a coverage area of the basestation. The present systems and methods may also allow a base stationto adjust its assignment of root sequences based on the root sequencesassigned to neighboring base stations.

The following description provides examples, and is not limiting of thescope, applicability, or configuration set forth in the claims. Changesmay be made in the function and arrangement of elements discussedwithout departing from the spirit and scope of the disclosure. Variousembodiments may omit, substitute, or add various procedures orcomponents as appropriate. For instance, the methods described may beperformed in an order different from that described, and various stepsmay be added, omitted, or combined. Also, features described withrespect to certain embodiments may be combined in other embodiments.

Referring first to FIG. 1, a diagram illustrates an example of awireless communications system 100. The system 100 includes basestations (or cells) 105, communication devices 115, and a core network130. The base stations 105 may communicate with the communicationdevices 115 under the control of a base station controller, which may bepart of the core network 130 or the base stations 105 in variousembodiments. Base stations 105 may communicate control informationand/or user data with the core network 130 through backhaul links 132.In some embodiments, the base stations 105 may communicate, eitherdirectly or indirectly, with each other over backhaul links 132, whichmay be wired or wireless communication links. The system 100 may supportoperation on multiple carriers (waveform signals of differentfrequencies). Multi-carrier transmitters may transmit modulated signalssimultaneously on the multiple carriers. For example, each communicationlink 125 may be a multi-carrier signal modulated according to variousradio technologies. Each modulated signal may be sent on a differentcarrier and may carry control information (e.g., reference signals,control channels, etc.), overhead information, data, etc.

The base stations 105 may wirelessly communicate with the devices 115via one or more base station antennas. Each of the base station 105sites may provide communication coverage for a respective geographicarea 110. In some embodiments, base stations 105 may be referred to as abase transceiver station, a radio base station, an access point, a radiotransceiver, a basic service set (BSS), an extended service set (ESS), aNodeB, an evolved NodeB (eNodeB or eNB), Home NodeB, a Home eNodeB, orsome other suitable terminology. The coverage area 110 for a basestation may be divided into sectors making up only a portion of thecoverage area. The system 100 may include base stations 105 of differenttypes (e.g., macro, micro, and/or pico base stations). There may beoverlapping coverage areas for different technologies.

In some embodiments, the system 100 may be an LTE/LTE-A network. InLTE/LTE-A networks, the terms evolved Node B (eNB) and user equipment(UE) may be generally used to describe the base stations 105 and devices115, respectively. The system 100 may be a Heterogeneous LTE/LTE-Anetwork in which different types of eNBs provide coverage for variousgeographical regions. For example, each eNB 105 may providecommunication coverage for a macro cell, a pico cell, a femto cell,and/or other types of cell. A macro cell generally covers a relativelylarge geographic area (e.g., several kilometers in radius) and may allowunrestricted access by UEs with service subscriptions with the networkprovider. A pico cell would generally cover a relatively smallergeographic area and may allow unrestricted access by UEs with servicesubscriptions with the network provider. A femto cell would alsogenerally cover a relatively small geographic area (e.g., a home) and,in addition to unrestricted access, may also provide restricted accessby UEs having an association with the femto cell (e.g., UEs in a closedsubscriber group (CSG), UEs for users in the home, and the like). An eNBfor a macro cell may be referred to as a macro eNB. An eNB for a picocell may be referred to as a pico eNB. And, an eNB for a femto cell maybe referred to as a femto eNB or a home eNB. An eNB may support one ormultiple (e.g., two, three, four, and the like) cells. In oneembodiment, an eNB 105 may set an initial Ncs parameter that defines ashift of root sequences. The root sequences may be available to UEs togenerate preambles to carry out a timing synchronization procedure withthe eNB 105. The eNB 105 may determine whether a count of timingsynchronization failures between itself and a UE 115 satisfies athreshold. If the number of failures satisfies the threshold, the eNB105 may dynamically adjust its initial Ncs parameter. By adjusting theNcs parameter, the assignment of root sequences to the eNB 105 changes.The eNB 105 may communicate these changes to a neighboring eNB. Theneighboring eNB may also determine whether to adjust its Ncs parameter(which would alter its assignment of root sequences). The neighboringeNB may then report its changes to another neighboring eNB. This processmay continue through each eNB in the system 100.

The core network 130 may communicate with the eNBs 105 via a backhaul132 (e.g., S1, etc.). The eNBs 105 may also communicate with oneanother, e.g., directly or indirectly via backhaul links 134 (e.g., X2,etc.) and/or via backhaul links 132 (e.g., through core network 130).The wireless system 100 may support synchronous or asynchronousoperation. For synchronous operation, the eNBs may have similar frametiming, and transmissions from different eNBs may be approximatelyaligned in time. For asynchronous operation, the eNBs may have differentframe timing, and transmissions from different eNBs may not be alignedin time. The techniques described herein may be used for eithersynchronous or asynchronous operations.

The UEs 115 may be dispersed throughout the wireless system 100, andeach UE may be stationary or mobile. A UE 115 may also be referred to bythose skilled in the art as a mobile station, a subscriber station, amobile unit, a subscriber unit, a wireless unit, a remote unit, a mobiledevice, a wireless device, a wireless communications device, a remotedevice, a mobile subscriber station, an access terminal, a mobileterminal, a wireless terminal, a remote terminal, a handset, a useragent, a mobile client, a client, or some other suitable terminology. AUE 115 may be a cellular phone, a personal digital assistant (PDA), awireless modem, a wireless communication device, a handheld device, atablet computer, a laptop computer, a cordless phone, a wireless localloop (WLL) station, or the like. A UE may be able to communicate withmacro eNBs, pico eNBs, femto eNBs, relays, and the like. In oneconfiguration, the UE 115 may maintain a log that includes a number oftiming synchronization failures that have occurred between the UE 115and an eNB 105. The UE 115 may process this log and transmit a report tothe eNB 105 indicating whether or not the Ncs parameter of the eNB 105should be adjusted. The UE 115 may also transmit the log withoutprocessing the log. The eNB 105 may then use the log to perform theprocessing to determine whether or not to adjust its Ncs parameter.

The transmission links 125 shown in network 100 may include uplinktransmissions from a mobile device 115 to a base station 105, and/ordownlink transmissions, from a base station 105 to a mobile device 115.The downlink transmissions may also be called forward link transmissionswhile the uplink transmissions may also be called reverse linktransmissions. While the wireless system 100 is described in relation toLTE/LTE-Advanced architectures, those skilled in the art will readilyappreciate, the various concepts presented throughout this disclosuremay be extended to other types of wireless networks.

FIG. 2 is a block diagram 200 illustrating one embodiment of an eNB105-a, in accordance with the present systems and methods. The eNB 105-amay be an example of the eNB 105 of FIG. 1. The eNB 105-a may include aneNB receiver module 205, an adjustment module 210, and an eNBtransmitter module 215. The eNB 105-a may be part of a Self OptimizedNetwork (SON). Each of these components may be in communication witheach other.

These components of the eNB 105-a may, individually or collectively, beimplemented with one or more application-specific integrated circuits(ASICs) adapted to perform some or all of the applicable functions inhardware. Alternatively, the functions may be performed by one or moreother processing units (or cores), on one or more integrated circuits.In other embodiments, other types of integrated circuits may be used(e.g., Structured/Platform ASICs, Field Programmable Gate Arrays(FPGAs), and other Semi-Custom ICs), which may be programmed in anymanner known in the art. The functions of each unit may also beimplemented, in whole or in part, with instructions embodied in amemory, formatted to be executed by one or more general orapplication-specific processors.

In one embodiment, the eNB receiver module 205 may receivecommunications from one or more UEs 115 and/or from one or more othereNBs. The adjustment module 210 may determine whether certain parametersof the eNB 105-a should be adjusted. For example, the eNB 105-a may setinitial parameters to use for wireless communications with the UEs 115.The adjustment module 210 may analyze the communications between the eNB105-a and the UEs 115 to determine whether one or more of theseparameters should be adjusted. The eNB transmitter module 215 maytransmit communications to one or more UEs 115 and/or to one or moreother eNBs. Further details regarding the adjustment module 210 of theeNB 105-a will be described below.

FIG. 3 is a block diagram 300 illustrating a further embodiment of aneNB 105-b, in accordance with the present systems and methods. The eNB105-b may be an example of the eNB 105 of FIGS. 1 and/or 2. The eNB105-b may include an eNB receiver module 205, an adjustment module210-a, and an eNB transmitter module 215. In one configuration, the eNB105-b may be part of a SON. Each of these components may be incommunication with each other.

These components of the eNB 105-b may, individually or collectively, beimplemented with one or more application-specific integrated circuits(ASICs) adapted to perform some or all of the applicable functions inhardware. Alternatively, the functions may be performed by one or moreother processing units (or cores), on one or more integrated circuits.In other embodiments, other types of integrated circuits may be used(e.g., Structured/Platform ASICs, Field Programmable Gate Arrays(FPGAs), and other Semi-Custom ICs), which may be programmed in anymanner known in the art. The functions of each unit may also beimplemented, in whole or in part, with instructions embodied in amemory, formatted to be executed by one or more general orapplication-specific processors.

The eNB receiver module 205 and the eNB transmitter module 215 mayoperate as previously described. The adjustment module 210-a may includean Ncs adjustment module 305 and a root sequence adjustment module 310.In one configuration, the Ncs adjustment module 305 may determinewhether a current Ncs parameter set at the eNB 105-b should be adjusted.Upon determining that an adjustment to the parameter should beperformed, the Ncs adjustment module 305 may adjust the parameter. Theroot sequence adjustment module 310 may determine whether to adjust theassignment of root sequences currently assigned to the eNB 105-b. In oneconfiguration, the root sequence adjustment module 310 may receiveinformation from the Ncs adjustment module 305. The received informationmay indicate the adjustment of the Ncs parameter. Upon receiving theadjustment information for the Ncs parameter, the root sequenceadjustment module 310 may adjust the assignment of root sequencescurrently assigned to the eNB 105-b. The eNB transmitter module 215 maytransmit information to neighboring eNBs indicating the adjustment ofthe root sequences assigned to the eNB 105-b.

FIG. 4 is a block diagram 400 illustrating a further embodiment of aneNB 105-c, in accordance with the present systems and methods. The eNB105-c may be an example of the eNB 105 of FIGS. 1, 2, and/or 3. The eNB105-c may include an eNB receiver module 205, an adjustment module210-b, and an eNB transmitter module 215. In one example, the eNB 105-cmay be part of a SON. Each of these components may be in communicationwith each other.

These components of the eNB 105-c may, individually or collectively, beimplemented with one or more application-specific integrated circuits(ASICs) adapted to perform some or all of the applicable functions inhardware. Alternatively, the functions may be performed by one or moreother processing units (or cores), on one or more integrated circuits.In other embodiments, other types of integrated circuits may be used(e.g., Structured/Platform ASICs, Field Programmable Gate Arrays(FPGAs), and other Semi-Custom ICs), which may be programmed in anymanner known in the art. The functions of each unit may also beimplemented, in whole or in part, with instructions embodied in amemory, formatted to be executed by one or more general orapplication-specific processors.

The eNB receiver module 205 and the eNB transmitter module 215 mayoperate as previously described. The adjustment module 210-b may includean Ncs adjustment module 305-a. In one configuration, the Ncs adjustmentmodule 305-a may include a preamble detection module 405, a timingestimation module 410, a counter module 415, and a comparison module420.

In one embodiment, the preamble detection module 405 may detect thereceipt of one or more preambles via the eNB receiver module 205. Apreamble may be sent as part of a first message (e.g., MSG1) from a UE115. The preamble may be a PRACH preamble sent by the UE 115 toinitialize a connection setup procedure with the eNB 105-c. The PRACHpreamble may be derived from a root sequence (e.g., a Zadoff-Chusequence). In one embodiment, there may be a total of 893 root sequencesavailable to generate PRACH preambles. In one configuration, the eNB105-c may configure the served UE 115 with the root sequence(s) fromwhich the UE 115 may generate 64 preambles to use as MSG1 of the RACHprocess. In order for eNBs to distinguish between different UEsinitializing a connection setup procedure, different PRACH preambles maybe transmitted by the different UEs. A UE may randomly pick a preambleout of a pool and transmit it to an eNB. In one embodiment, each cell ofan eNB 105, may include 64 RACH preambles that are available for the UEto choose from.

Upon detecting the receipt of a preamble, the preamble detection module405 may perform a mathematical correlation for the received signal andset of root sequences to determine which preamble ID (or sequence) wasdetected. When the module 405 identifies a match (or a partial match)between the detected preamble and a reference root sequence, thepreamble detection module 405 may generate a preamble identification(ID). The preamble ID may represent the preamble that the eNB 105-cbelieves was selected and transmitted by the UE 115 to initialize theconnection setup procedure. The “preamble ID” may be a conventionalnaming used in 3GPP standards to identify a certain root sequence. Thepreamble ID may also be relative to the base sequence (also referred toas a PRACH physical root) that is configured by the eNB.

PRACH physical roots may also be mapped in 3GPP specifications throughone or more tables to PRACH logical roots. In one embodiment, PRACHlogical roots may allow a UE 115 to derive the order of which physicalroots are being used. For example, if the number of required physicalroots is “X” for a certain Ncs value, the eNB 105-c may indicate onlythe first logical root to the UE. The UE may derive the actual physicalroots and their usage order by utilizing the defined 3GPP standard.

In one configuration, the timing estimation module 410 may estimate atiming advanced (TA) value that estimates the propagation delay betweenthe eNB 105-c and the UE that 115 sent the preamble. As a result, the TAmay represent the distance from the eNB 105-c or the relativegeographical region of the coverage area of the eNB 105-c, as perceivedby the eNB 105-c, from which the preamble originated. For example, alarge TA may indicate that the eNB 105-c perceives that the UE 115 thatsent the preamble is located farther away from the eNB 105-c. The eNBtransmitter module 215 may transmit a second message (e.g., MSG2) to theUE 115. The second message may include the preamble ID and the TA valueestimated by the eNB 105-c. When the eNB 105-c detects a certainpreamble ID and estimates the TA value, the eNB may communicate thisinformation, along with other information, to the UE 115 utilizing MSG2.

In one example, the counter module 415 may maintain a count of thenumber of times a third message (e.g., MSG3) is not received after thesecond message is transmitted to the UE 115. In one embodiment, when theUE 115 receives the second message with the preamble ID and TA value,the UE 115 may analyze the preamble ID to determine whether the preambleID identifies the correct preamble that was selected and transmitted bythe UE 115 as part of the first message. If the UE 115 determines thatthe preamble ID incorrectly identifies the preamble, the UE 115 mayabort the transmission of the third message. In one configuration, theUE 115 may attempt to initialize MSG1 transmission again.

When the counter module 415 detects a non-receipt of the third message,the module 415 may analyze the TA value that was sent with the preambleID. If the TA value represents a certain geographical area of the cell(or certain distance relative to the cell), the counter module 415 mayincrease a counter. For example, if the TA value is small (indicatingthat the eNB 105-c perceives that the first message with the preamblewas received from a UE 115 located relatively close to the eNB 105-c),the counter module 415 may increase the counter when it determines thatthe third message is not received from the UE 115. The comparison module420 may compare the counter with a threshold value. When the counter fora certain area of the cell satisfies the threshold value, the Ncsadjustment module 305-a may adjust the current Ncs parameter of the eNB105-c.

In one configuration, the adjustment module 210-b may also include aroot sequence adjustment module 310-a. The module 310-a may include aninsertion module 425, an extraction module 430, and a root sequenceanalysis module 435. In one embodiment, the insertion module 425 mayinsert information regarding the current assignment of root sequences tothe eNB 105-c into a token. In one embodiment, if the Ncs parameter isadjusted by the Ncs adjustment module, the root sequences assigned tothe eNB 105-c will also be adjusted. The insertion module 425 may insertthe updated assignments of root sequences into the token. The extractionmodule 430 may extract information from a token received from aneighboring eNB. The root sequence analysis module 435 may analyze theextracted information to determine the root sequences assigned to theneighbor eNB that sent the token. Based on this analysis, the rootsequence adjustment module 310-a may adjust the current assignment ofroot sequences assigned to the eNB 105-c based on the root sequencesassigned to the neighboring eNB. Upon adjusting the root sequenceassignment, the eNB 105-c may determine whether its Ncs parameter shouldbe adjusted. If the Ncs parameter is adjusted, the assignment of rootsequences to the eNB 105-c are again updated and the updated assignmentinformation is inserted into the token by the insertion module 425. Thetoken may then be transmitted via the eNB transmitter module 215 toanother neighboring eNB.

In one embodiment, the receipt of the token may trigger an eNB todetermine whether to adjust its Ncs parameter. In one configuration, theeNB may perform this determination after receiving the token. eNBs thatdo not have the token, may not carry out the procedure to determinewhether their Ncs parameters should be adjusted. Other approaches may bealso used without using an explicit token. For example a centralizedserver may be used, or a predefined order of eNBs may be used todetermine which eNB should perform the procedure to determine whether toadjust its Ncs parameter. In addition, this process of determiningwhether to adjust an Ncs parameter may be ran at each eNB or at acentralized processing unit or server. This process may also beperformed via simulation tools or network planning software with or without direct interaction with components of a live network (e.g., eNBs,UEs, etc.).

In one embodiment, a last used logical root (LULR), as defined in thisdisclosure, may represent the logical root value that corresponds to thelast physical root sequence used in a certain eNB. In one example, LULRmay be mapped to a starting physical root, as described in 3GPPstandards. As previously explained, in LTE there are 839 physical rootsthat may be used to generate preambles (i.e., MSG1). Neighbor eNBs,however, should not use the same physical roots. When eNBs are separatedby a long distance (e.g., where path loss attenuation allows to mitigatethe potential interference), they may use the same root sequences.

As a results of Ncs dimensioning of the present systems and methods, thenumber of required physical roots at each eNB may change. To ensure thatall the physical roots are being utilized after changes to Ncsparameters occur, a Logical Roots Packing Algorithm may be used by theroot sequence adjustment module 310-b. In one embodiment, the LULR for aprevious eNB may be extracted from a received token via the extractionmodule 430. The new logical root may be adjusted according to equation1:Lseq_new=LULR+Dv  Equation 1

In one embodiment, Dv may represent a packing distance between rootsassigned to different eNBs. Dv may be positive value, a negative value,or zero. In one configuration, Dv=0 may indicate that an overlap existswith the last used logical root and a root sequence used by another eNB.A Dv value of 1 may indicate that no overlap exists. The magnitude of Dvin the positive direction may indicate the gap between the last usedlogical root of the eNB 105-c and the root sequence assigned to theneighboring eNB. The magnitude of the Dv in the negative direction mayindicate the amount of overlap of the last used logical root of the eNB105-c and root sequences assigned to the neighboring eNB.

FIG. 5 is a message flow diagram 500 of a connection setup procedurebetween an eNB 105-d and a UE 115. The eNB 105-d may be an example ofthe eNB 105 of FIGS. 1, 2, 3, and/or 4. The UE 115 may be an example ofthe UE 115 of FIG. 1. The message flows may occur in a SON.

In LTE, the UE 115 may acquire initial timing synchronization byperforming a RACH procedure. The UE 115 may transmit a first MSG1preamble 505-a-1. The first MSG1 preamble may be derived from aZadoff-Chu sequence. UE may discover available preambles to choose frombased on a system information block (SIB) broadcasted in the cell of theeNB 105-d.

When the eNB 105-d detects the MSG1 preamble 505-a-1, it may estimatethe UE's time advanced and the detected preamble ID. The eNB 105-d mayrespond to the UE 115 by transmitting a first MSG2 510-a-1. The firstMSG2 may include the estimated TA value and the detected preamble ID. Ifthe UE 115 is able to decode MSG2 correctly, it may use the TAestimation to adjust the timing of a MSG3. However, if the eNB 105-dincorrectly detected the preamble ID of the first MSG1 preamble 505-a-1,the eNB 105-d may communicate the non-matching preamble ID and wrong TAestimation to the UE 115. When the UE 115 decodes MSG2, it may eitherfail to match the preamble ID included in MSG2 with the one originallysent in MSG1. When this occurs, the UE 115 may not respond with the MSG3and the eNB 105-d may detect 515-a-1 a non-receipt of MSG3.

When MSG3 is not received, this trial of the RACH procedure may beconsidered as a timing synchronization failure. If the preamble ID isincorrectly detected by the eNB 105-d, the estimation of the TA valuemay also be incorrect. If the UE 115 were to transmit MSG3 using theincorrect TA, MSG3 may not have the correct uplink timing adjustment andhence the uplink transmission to the eNB 105-d might fail. In oneconfiguration, the eNB 105-d may record each detected preamble ID andthe corresponding TA value. The eNB 105-d may also record whether eachRACH trial passed or failed.

Using this information, the eNB 105-d may determine which range of TAvalues is experiencing a high failure rate, as well as the maximum cellrange from which a UE 115 is attempting to send a MSG1. In one example,the eNB 105-d may determine 520 whether a number of MSG3 non-receipts(i.e., RACH trial failures, timing synchronization failures, etc.)exceed a threshold for a particular TA value or range of TA values. Ifthe threshold is exceeded, the eNB 105-d may adjust 525 the Ncsparameter.

FIG. 6 is a block diagram 600 illustrating one embodiment of a coveragearea of a cell of an eNB 105-e. The eNB 105-e may be an example of theeNB 105 of FIGS. 1, 2, 3, 4, and/or 5. The eNB 105-e may support variouscoverage based on the Ncs parameter being implemented by the eNB 105-e.In one configuration, the current Ncs parameter may allow the eNB 105-eto support a first area 605, a second area 610, and a third area 615.The third area 615 may be the maximum distance supported by the currentNcs configuration at the eNB 105-e. The eNB 105-e may incorrectly detectpreambles (e.g., MSG1 RACH preambles) that are transmitted at distancesgreater than the third area 615.

In one embodiment, the eNB 105-e may have a repeating observation periodto detect PRACH preambles. The length of the observation period may bebased on the coverage area of the eNB 105-e that is supported by thecurrent Ncs configuration. The eNB 105-e may determine that preamblesreceived closer to the start of the observation period were originatedfrom UEs that are located close to the eNB 105-e, while preamblesreceived closer to the end of the observation period were originatedfrom UEs located at the edge of the cell's Ncs coverage area (e.g., atthe edge of the third coverage area 615).

As an example, the eNB 105-e may have a repeating observation period of2 microseconds. The eNB 105-e may estimate the TA value based on when apreamble is received during an observation period. Available preamblesfor UEs to choose from may include “12345”, “51234”, “45123”, etc. Afirst UE may transmit a preamble (e.g., “12345”) from the first coveragearea 605. This close distance to the eNB 105-e may reduce the latency ofthe transmission. Thus, the entire preamble may be received at the eNB105-e early on during the observation period. The eNB 105-e may comparethe received preamble against reference codes. The eNB 105-e maydetermine that the preamble “12345” matches the reference code “12345”,and may generate a preamble ID indicates that indicates the eNB 105-ereceived the preamble “12345”. The eNB 105-e may also calculate the TAvalue for subsequent transmissions sent from the first UE. The TA valuemay be estimated based on when the preamble was received during theobservation period.

A second UE may transmit a preamble (e.g., “51234”) from the secondcoverage area 610. This preamble may be received later on during theobservation window. Because the second UE is also located in the Ncscoverage area, the eNB 105-e may receive the entire preamble (e.g.,51234″) during the observation period. The eNB 105-e may again comparethis preamble against a set of reference codes and may determine thatthe preamble “51234” matches the reference code “51234”. A preamble IDmay be generated that informs the second UE that the eNB 105-e receivedthe preamble “51234”. The eNB 105-e may also calculate a different TAvalue for the second UE. The TA value may be different to account forthe latency of the transmissions between the second UE and the eNB105-e.

A third UE, which is out of the Ncs coverage area of the eNB 105-e(e.g., the UE 115 may be located beyond the third coverage area 615),may transmit a preamble (“45123”) that is derived from a root sequencewith a cyclic shift indicated by the current Ncs value. Because thethird UE is out of the Ncs coverage area associated with the current Ncsvalue, the cyclic shift of the preamble may be too short. In thisexample, the eNB 105-e may receive the preamble 2.1 microseconds afterit was transmitted from the UE. Thus, the preamble is not receivedduring a first observation period of 2 microseconds, but is received 0.1microseconds after a second observation period has begun. In oneexample, part of the preamble (e.g., “45”) may be received at the end ofthe first observation period and the remaining portion of the preamble(e.g., “123”) may be received at the beginning of the second observationperiod. The eNB 105-e may not use information that was received duringprevious observation period. Thus, from the view point of the eNB 105-e,it has received a preamble of “123” at the beginning of an observationperiod (the parts “45” of the preamble being received during theprevious observation period.) The eNB 105-e may then compare referencecodes against the received preamble “123”. The eNB 105-e may determinethat the received preamble of “123” closely matches the reference code“12345”. As a result, the eNB 105-e may incorrectly conclude that thethird UE transmitted the preamble “12345” and may generate a preamble IDthat indicates to the third UE that the eNB 105-e believes it hasreceived preamble “12345”. Further, because the eNB 105-e believes thepreamble was received at the beginning of an observation period (i.e.,the second observation period), the eNB 105-e may calculate a TA valueas if the third UE were located within the first coverage area 605. TheTA value informs the UE how to adjust its timing for futuretransmissions on the uplink to the eNB 105-e.

The calculated preamble ID and TA value are transmitted back to the UE.The UE may analyze the preamble ID and determine that the preamble IDwas incorrectly detected by the eNB 105-e. As a result, the UE may abortthe transmission of a subsequent message. The eNB 105-e may detect thenon-receipt of this subsequent message and may increase a counter oftiming synchronization failures. The counter may indicate the number offailures (non-receipt of MSG3 from UE) that have occurred when the TAvalues suggest that the preambles originated from UE(s) located in, forexample, the first coverage area 605. When the counter satisfies athreshold, the Ncs value of the eNB 105-e may be adjusted. In oneexample, if the eNB 105-e detects a high number of timingsynchronization failures are occurring with TA values indicating thepreambles were allegedly sent from UEs located nearby the eNB 105-e, theeNB 105-e may determine that the UEs that sent these preambles areactually located beyond the Ncs coverage area. As a result, the eNB105-e may adjust the current Ncs parameter to increase the cyclic shiftof the root sequences assigned to the eNB 105-e. Configuring Ncs to ahigher value may allow the coverage area of the eNB 105-e to expand.This may, in turn, allow the UEs to perform successful RACH processeswithin the new Ncs value.

In one embodiment, if the eNB 105-e determines that a number of timingsynchronization failures corresponding with a range of TA values for thefirst coverage area 605 does not exceed the threshold, the eNB 105-e mayadjust the current Ncs parameter to a lower value in order to reduce thecyclic shift length applied to the base root sequences assigned to theeNB 105-e. Decreasing the cyclic shift may decrease the coverage area ofthe eNB 105-e supported by the Ncs configuration. The Ncs value maycontinue to be adjusted until the number of failures corresponding tothe range of TA values for the first coverage area does exceed thethreshold. When this occurs, the Ncs value may be adjusted to increasethe coverage area and the eNB 105-e may use an optimal Ncsconfiguration.

FIG. 7 is a block diagram 700 illustrating one embodiment of a UE 115-a,in accordance with the present systems and methods. The UE 115-a may bean example of the UE 115 of FIGS. 1 and/or 5. The UE 115-a may include aUE receiver module 705, a reporting module 710, and a UE transmittermodule 715. In one example, the UE 115-a may be part of a SON. Each ofthese components may be in communication with each other.

These components of the UE 115-a may, individually or collectively, beimplemented with one or more application-specific integrated circuits(ASICs) adapted to perform some or all of the applicable functions inhardware. Alternatively, the functions may be performed by one or moreother processing units (or cores), on one or more integrated circuits.In other embodiments, other types of integrated circuits may be used(e.g., Structured/Platform ASICs, Field Programmable Gate Arrays(FPGAs), and other Semi-Custom ICs), which may be programmed in anymanner known in the art. The functions of each unit may also beimplemented, in whole or in part, with instructions embodied in amemory, formatted to be executed by one or more general orapplication-specific processors.

In one embodiment, the UE receiver module 705 may receive communicationsfrom one or more other UEs and/or from one or more eNBs 105. Thereporting module 710 may collect and reporting information indicatingwhether certain parameters of an eNB 105 should be adjusted. Forexample, the eNB 105-a may set initial parameters to use for wirelesscommunications with the UEs 115. The reporting module 710 may gathervarious types of measurement information and communicate suchinformation to the eNB 105 via the UE transmitter module 715. The eNB105 may use the information to determine whether one or more of theseparameters should be adjusted. Further details regarding the reportingmodule 710 of the UE 115-a will be described below.

FIG. 8 is a block diagram 800 illustrating one embodiment of a UE 115-b,in accordance with the present systems and methods. The UE 115-b may bean example of the UE 115 of FIGS. 1, 5, and/or 7. The UE 115-b mayinclude a UE receiver module 705, a reporting module 710-a, and a UEtransmitter module 715. Each of these components may be in communicationwith each other.

These components of the UE 115-b may, individually or collectively, beimplemented with one or more application-specific integrated circuits(ASICs) adapted to perform some or all of the applicable functions inhardware. Alternatively, the functions may be performed by one or moreother processing units (or cores), on one or more integrated circuits.In other embodiments, other types of integrated circuits may be used(e.g., Structured/Platform ASICs, Field Programmable Gate Arrays(FPGAs), and other Semi-Custom ICs), which may be programmed in anymanner known in the art. The functions of each unit may also beimplemented, in whole or in part, with instructions embodied in amemory, formatted to be executed by one or more general orapplication-specific processors.

In one configuration, the reporting module 710-a may include a failurereporting module 805. The module 805 may maintain a log of timingsynchronization failures that occur between the UE 115-b and an eNB 105during a RACH procedure. The reporting module 710-a may also include aTA reporting module 810. The TA reporting module 810 may record the TAvalues received from the eNB 105 during a RACH trial. The reportingmodule 710-a may group together the logged timing synchronizationfailures with the corresponding TA value. The UE 115-b may generate areport indicating the number of failures and the corresponding TA valuesfor each failure. The report may also indicate the number of successfulRACH trials and the corresponding TA values. The report may betransmitted to the eNB 105 via the UE transmitter module 715.

FIG. 9 is a block diagram 900 illustrating one embodiment of a UE 115-c,in accordance with the present systems and methods. The UE 115-c may bean example of the UE 115 of FIGS. 1, 5, 7, and/or 8. The UE 115-c mayinclude a UE receiver module 705, a reporting module 710-b, and a UEtransmitter module 715. Each of these components may be in communicationwith each other.

These components of the UE 115-c may, individually or collectively, beimplemented with one or more application-specific integrated circuits(ASICs) adapted to perform some or all of the applicable functions inhardware. Alternatively, the functions may be performed by one or moreother processing units (or cores), on one or more integrated circuits.In other embodiments, other types of integrated circuits may be used(e.g., Structured/Platform ASICs, Field Programmable Gate Arrays(FPGAs), and other Semi-Custom ICs), which may be programmed in anymanner known in the art. The functions of each unit may also beimplemented, in whole or in part, with instructions embodied in amemory, formatted to be executed by one or more general orapplication-specific processors.

In one configuration, the reporting module 710-b may include a failurereporting module 805-a. The module 805-a may include a preamble IDdetection module 905, a preamble ID logging module 910, and a preambleID analysis module 915. In one configuration, the preamble ID detectionmodule 905 may detect the receipt of MSG2 from the eNB 105. The MSG2 mayinclude the preamble ID sent from the eNB 105. As previously explained,the preamble ID may indicate the preamble the eNB 105 determined wastransmitted from the UE 115-c as MSG1. The preamble ID logging module910 may log the detected preamble IDs. In one embodiment, the preambleID analysis module 915 may determine whether the detected preamble IDcorrectly identifies the preamble that was transmitted as MSG1.

The reporting module 710-b may also include a TA reporting module 810-a.The TA reporting module 810-a may include a TA detection module 920, aTA logging module 925, and a TA analysis module 930. In one example, theTA detection module 920 may detect the TA value that is received fromthe eNB 105 as part of MSG2. The TA logging module 925 may log thedetected TA values. In one example, the TA values may be logged with thecorresponding preamble ID that was received as part of the same MSG2from the eNB 105. The TA analysis module 930 may analyze the detected TAvalues to determine a number of TA values representing coverage areasnear the eNB 105. For the example, the analysis module 930 may identifythe TA values corresponding to the first coverage area 605 of the eNB105.

In one embodiment, the reporting module 710-b may transmit a report tothe eNB 105. The report may include information indicating the number oftiming synchronization failures (e.g., the number of occurrences whenthe UE 115-c did not transmit a MSG3 upon receipt of the preamble ID).The report may also indicate the number of failures that occurred withina certain Ncs coverage area of the eNB 105. In one embodiment, the UE115-c may analyze the report data to determine whether the eNB 105should adjust its Ncs parameter. In another embodiment, the UE 115-c maytransmit the report and the eNB 105 may perform the processing of thereport to determine whether it should change its Ncs parameter. Thereport may be sent passively to the eNB 105 (e.g., transmit the reportaccording to a timing cycle). The report may also be sent actively tothe eNB 105 when the UE 115-c receives a request to transmit the reportfrom the eNB 105. In one configuration, the report may be transmittedvia the UE transmitter module 715.

The module 805 may maintain a log of timing synchronization failuresthat occur between the UE 115-b and an eNB 105 during a RACH procedure.The reporting module 710-a may also include a TA reporting module 810.The TA reporting module 810 may record the TA values received from theeNB 105 during a RACH trial. The reporting module 710-a may grouptogether the logged timing synchronization failures with thecorresponding TA value. The UE 115-b may generate a report indicatingthe number of failures and the corresponding TA values for each failure.The report may also indicate the number of successful RACH trials andthe corresponding TA values. The report may be transmitted to the eNB105 via the UE transmitter module 715.

FIG. 10 is a message flow diagram 1000 of a connection setup procedurebetween a UE 115-d and an eNB 105. The UE 115-d may be an example of theUE of FIGS. 1, 5, 7, 8, and/or 9. The eNB 105 may be an example of theeNB 105 of FIGS. 1, 2, 3, 4, 5, and/or 6.

In one configuration, the UE 115-d may transmit a first MSG1 1005-a-1 tothe eNB 105. MSG1 may include a preamble, such as a PRACH preamble toinitialize the connection setup procedure. The eNB 105 may respond witha first MSG2 1010-a-1 that includes a preamble ID for the receivedpreamble and a TA estimation. The UE 115-d may be unable to correctlydecode MSG2 because the preamble ID was incorrectly detected by the eNB105. As a result, the UE 115-d may abort 1015-a-1 the transmission ofMSG3 to the eNB 105. This process may continue and the UE 115-d maycontinue to abort MSG3 transmissions if it is unable to decode MSG2received from the eNB 105. In one embodiment, the UE 115-d may transmita timing synchronization report 1020 to the eNB 105. The report 1020 mayinclude a log of the MSG1 preambles and the corresponding MSG2 preambleIDs. The report 1020 may further include a log of the TA estimationscorresponding to each MSG2 preamble ID. Further, the report may indicatewhether each particular MSG1/MSG2 pair resulted in a timingsynchronization failure (e.g., non-transmission of MSG3). The report1020 may also include an indication as to whether the eNB 105 shouldadjust its Ncs value. For example, the report may include one or morebits indicating to the eNB 105 that the Ncs parameter should beadjusted. In another embodiment, the report 1020 may include theinformation and the eNB 105 may process to information to determinewhether to modify its current Ncs configuration.

FIG. 11 is a block diagram of a MIMO communication system 1100 includingan eNB 105-f and an UE 115-e. This system 1100 may illustrate aspects ofthe system 100 of FIG. 1. The eNB 105-f may be an example of the eNB 105of FIGS. 1, 2, 3, 4, 5, 6, and/or 10. The UE 115-e may be an example ofthe UE 115 of FIGS. 1, 5, 7, 8, 9, and/or 10. The eNB 105-f may beequipped with antennas 1134-a through 1134-x, and the UE 115-e may beequipped with antennas 1152-a through 1152-n. In the system 1100, theeNB 105-f may be able to send data over multiple communication links atthe same time. Each communication link may be called a “layer” and the“rank” of the communication link may indicate the number of layers usedfor communication. For example, in a 2×2 MIMO system where eNB 105-ftransmits two “layers,” the rank of the communication link between theeNB 105-f and the UE 115-e is two.

At the eNB 105-f, a transmit processor 1120 may receive data from a datasource. The transmit processor 1120 may process the data. The transmitprocessor 1120 may also generate reference symbols, and a cell-specificreference signal. A transmit (TX) MIMO processor 1130 may performspatial processing (e.g., precoding) on data symbols, control symbols,and/or reference symbols, if applicable, and may provide output symbolstreams to the transmit modulators 1132-a through 1132-x. Each modulator1132 may process a respective output symbol stream (e.g., for OFDM,etc.) to obtain an output sample stream. Each modulator 1132 may furtherprocess (e.g., convert to analog, amplify, filter, and upconvert) theoutput sample stream to obtain a downlink signal. In one example,downlink signals from modulators 1132-a through 1132-x may betransmitted via the antennas 1134-a through 1134-x, respectively.

At the UE 115-e, the UE antennas 1152-a through 1152-n may receive thedownlink signals from the eNB 105-f and may provide the received signalsto the demodulators 1154-a through 1154-n, respectively. Eachdemodulator 1154 may condition (e.g., filter, amplify, downconvert, anddigitize) a respective received signal to obtain input samples. Eachdemodulator 1154 may further process the input samples (e.g., for OFDM,etc.) to obtain received symbols. A MIMO detector 1156 may obtainreceived symbols from all the demodulators 1154-a through 1154-n,perform MIMO detection on the received symbols if applicable, andprovide detected symbols. A receive processor 1158 may process (e.g.,demodulate, deinterleave, and decode) the detected symbols, providingdecoded data for the UE 115-e to a data output, and provide decodedcontrol information to a processor 1180, or memory 1182. In oneembodiment, the processor 1180 may include a reporting module 710-c toimplement the systems and methods described herein. The reporting module710-c may be examples of the module 710 of FIGS. 7, 8, and/or 9.

On the uplink, at the UE 115-e, a transmit processor 1164 may receiveand process data from a data source. The transmit processor 1164 mayalso generate reference symbols for a reference signal. The symbols fromthe transmit processor 1164 may be precoded by a transmit MIMO processor1166 if applicable, further processed by the demodulators 1154-a through1154-n (e.g., for SC-FDMA, etc.), and be transmitted to the eNB 105-f inaccordance with the transmission parameters received from the eNB 105-e.At the eNB 105-f, the uplink signals from the UE 115-e may be receivedby the antennas 1134, processed by the demodulators 1132, detected by aMIMO detector 1136 if applicable, and further processed by a receiveprocessor. The receive processor 1138 may provide decoded data to a dataoutput and to the processor 1140. The processor 1140 may include anadjustment module 210-c to implement the systems and methods describedherein. The module 210-c may be an example of the adjustment module 210of FIGS. 2, 3, and/or 4. The components of the UE 115-e may,individually or collectively, be implemented with one or moreApplication Specific Integrated Circuits (ASICs) adapted to perform someor all of the applicable functions in hardware. Each of the notedmodules may be a means for performing one or more functions related tooperation of the system 1100.

Similarly, the components of the eNB 105-f may, individually orcollectively, be implemented with one or more Application SpecificIntegrated Circuits (ASICs) adapted to perform some or all of theapplicable functions in hardware. Each of the noted components may be ameans for performing one or more functions related to operation of thesystem 1100.

The communication networks that may accommodate some of the variousdisclosed embodiments may be packet-based networks that operateaccording to a layered protocol stack. For example, communications atthe bearer or Packet Data Convergence Protocol (PDCP) layer may beIP-based. A Radio Link Control (RLC) layer may perform packetsegmentation and reassembly to communicate over logical channels. AMedium Access Control (MAC) layer may perform priority handling andmultiplexing of logical channels into transport channels. The MAC layermay also use Hybrid ARQ (HARQ) to provide retransmission at the MAClayer to improve link efficiency. At the Physical layer, the transportchannels may be mapped to Physical channels.

FIG. 12 is a flow chart illustrating one embodiment of a method 1200 foradjusting an Ncs parameter. For clarity, the method 1200 is describedbelow with reference to the eNB 105 of FIGS. 1, 2, 3, 4, 5, 6, 10 and/or11. In one implementation, the adjustment module 210 of FIGS. 2, 3, 4,and/or 11 may execute one or more sets of codes to control thefunctional elements of the eNB 105 to perform the functions describedbelow.

At block 1205, an initial Ncs parameter may be set. At block 1210, adetermination may be made as to whether a count of timingsynchronization failures between a mobile device (e.g., a UE 115) and abase station (e.g., an eNB 105) exceed a threshold. Upon determiningthat the count of timing synchronization failures satisfies thethreshold, at block 1215, the initial Ncs parameter may be dynamicallyadjusted.

Therefore, the method 1200 may provide for dynamically adjusting aninitial Ncs value based on a number of timing synchronization failuresthat occur between the UE 115 and the eNB 105. It should be noted thatthe method 1200 is just one implementation and that the operations ofthe method 1200 may be rearranged or otherwise modified such that otherimplementations are possible.

FIG. 13 is a flow chart illustrating one embodiment of a method 1300 formaintaining a counter of timing synchronization failures to determinewhether to adjust an Ncs parameter. For clarity, the method 1300 isdescribed below with reference to the eNB 105 of FIGS. 1, 2, 3, 4, 5, 6,10 and/or 11. In one implementation, the adjustment module 210 of FIGS.2, 3, 4, and/or 11 may execute one or more sets of codes to control thefunctional elements of the eNB 105 to perform the functions describedbelow.

At block 1305, a first message including a preamble may be received. Thepreamble may be a PRACH preamble used to initialize a RACH procedure. Atblock 1310, a preamble ID may be generated for the received preamble.The preamble ID may be generated by comparing the received preamble withone or more reference codes. The reference code that matches thereceived preamble with a certain degree of accuracy may be used as thepreamble ID. At block 1315, a second message may be transmitted thatincludes the preamble ID. At block 1320, a determination may be made asto whether a third message is received in response to the secondmessage. If it is determined that the third message is received, thethird message may be processed at block 1325. If, however, it isdetermined that the third message is not received, a counter of timingsynchronization failures may be increased 1330.

Therefore, the method 1300 may provide for maintaining a counter oftiming failures that occur between the UE 115 and the eNB 105. It shouldbe noted that the method 1300 is just one implementation and that theoperations of the method 1300 may be rearranged or otherwise modifiedsuch that other implementations are possible.

FIG. 14 is a flow chart illustrating one embodiment of a method 1400 foradjusting an Ncs parameter based on a number of timing synchronizationfailures that occur within a certain Ncs coverage area of an eNB 105.For clarity, the method 1400 is described below with reference to theeNB 105 of FIGS. 1, 2, 3, 4, 5, 6, 10 and/or 11. In one implementation,the adjustment module 210 of FIGS. 2, 3, 4, and/or 11 may execute one ormore sets of codes to control the functional elements of the eNB 105 toperform the functions described below.

At block 1405, a first message including a PRACH preamble may bereceived. At block 1410, a preamble ID for the received PRACH preamblemay be generated. At block 1415, a TA value may be estimated for thereceived PRACH preamble. The TA value may be generated by the eNB 105 toindicate to the UE 115 how to adjust its uplink timing for subsequentmessages. Thus, the TA value indicates where the eNB 105 believes the UE115 to be located within the Ncs coverage area.

At block 1425, a determination may be made as to whether a third messageis received in response to the second message. If it is determined thatthe third message is received, the third message may be processed atblock 1430. If, however, it is determined that the third message is notreceived, a determination 1435 may be made as to whether the TA valuecorresponds to an inner coverage area of the Ncs coverage area (e.g.,the first coverage area 605). If it is determined that the TA value doesnot correspond to the inner coverage area, the method 1400 may return toreceive a first message with a PRACH preamble at block 1405. If,however, it is determined that the TA value does correspond to the innercoverage area, at block 1440, a counter of timing synchronizationfailures may be increased. At block 1445, timing synchronizationfailures (i.e., communication failures) may be correlated with TAestimated values. In one example, communication failures may beclassified into a range of estimated TA values. As a result, the eNB 105may determine the number of communication failures that have occurredfor any range of TA estimated values. A determination 1450 may be madeas to whether the count of failures satisfies a threshold. If it isdetermined that the count does not exceed the threshold, the method 1400may return to receive a first message with a PRACH preamble at block1405. If, however, it is determined that the count of timingsynchronization failures does exceed the threshold, at block 1455, anNcs parameter may be adjusted.

Therefore, the method 1400 may provide for adjusting an Ncs parameterbased on a number of timing synchronization failures that occur within acertain Ncs coverage area of an eNB 105. It should be noted that themethod 1400 is just one implementation and that the operations of themethod 1400 may be rearranged or otherwise modified such that otherimplementations are possible.

FIG. 15 is a flow chart illustrating one embodiment of a method 1500 fordynamically adjusting an assignment of root sequences used to derivepreambles across a plurality of eNBs 105. For clarity, the method 1500is described below with reference to the eNB 105 of FIGS. 1, 2, 3, 4, 5,6, 10 and/or 11. In one implementation, the adjustment module 210 ofFIGS. 2, 3, 4, and/or 11 may execute one or more sets of codes tocontrol the functional elements of the eNB 105 to perform the functionsdescribed below.

At block 1505, a token may be received from a second eNB (i.e., basestation). At block 1510, information may be extracted from the token.The information may indicate an assignment of one or more root sequencesassigned to the second eNB. At block 1515, an assignment of one or moreroot sequences assigned to the eNB may be adjusted based on theextracted information. At block 1520, a procedure to determine whetherto adjust a current Ncs configuration of the eNB may be executed. If theNcs is adjusted, the root sequence assignment may be further adjusted.At block 1525, information may be inserted into the token. Theinformation may indicate the assignment of the one or more rootsequences assigned to the eNB. At block 1530, the token may be releasedto a third eNB.

Therefore, the method 1500 may provide for dynamically adjusting anassignment of root sequences used to derive preambles across a pluralityof eNBs 105. It should be noted that the method 1500 is just oneimplementation and that the operations of the method 1500 may berearranged or otherwise modified such that other implementations arepossible.

FIG. 16 is a flow chart illustrating one embodiment of a method 1600 formaintaining a log of timing synchronization failures to report to an eNB105. For clarity, the method 1600 is described below with reference tothe UE 115 of FIGS. 1, 5, 7, 8, 9, 10 and/or 11. In one implementation,the reporting module 710 of FIGS. 7, 8, 9, and/or 10 may execute one ormore sets of codes to control the functional elements of the UE 115 toperform the functions described below.

At block 1605, a first message may be transmitted to an eNB thatincludes a preamble. At block 1610, a second message may be receivedfrom the eNB that includes a preamble ID. At block 1615, a log may bemaintained that indicates whether a transmission of a third message tothe eNB is aborted. At block 1620, a report may be transmitted to theeNB. The report may include a log of timing synchronization failures.The report may be used by the eNB to determine whether to adjust an Ncsparameter.

Therefore, the method 1600 may provide for maintaining a log of timingsynchronization failures to report to an eNB 105. It should be notedthat the method 1600 is just one implementation and that the operationsof the method 1600 may be rearranged or otherwise modified such thatother implementations are possible.

Techniques described herein may be used for various wirelesscommunications systems such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, andother systems. The terms “system” and “network” are often usedinterchangeably. A CDMA system may implement a radio technology such asCDMA2000, Universal Terrestrial Radio Access (UTRA), etc. CDMA2000covers IS-2000, IS-95, and IS-856 standards. IS-2000 Releases 0 and Aare commonly referred to as CDMA2000 1×, 1×, etc. IS-856 (TIA-856) iscommonly referred to as CDMA2000 1×EV-DO, High Rate Packet Data (HRPD),etc. UTRA includes Wideband CDMA (WCDMA) and other variants of CDMA. ATDMA system may implement a radio technology such as Global System forMobile Communications (GSM). An OFDMA system may implement a radiotechnology such as Ultra Mobile Broadband (UMB), Evolved UTRA (E-UTRA),IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDM, etc.UTRA and E-UTRA are part of Universal Mobile Telecommunication System(UMTS). 3GPP Long Term Evolution (LTE) and LTE-Advanced (LTE-A) are newreleases of UMTS that use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A, andGSM are described in documents from an organization named “3rdGeneration Partnership Project” (3GPP). CDMA2000 and UMB are describedin documents from an organization named “3rd Generation PartnershipProject 2” (3GPP2). The techniques described herein may be used for thesystems and radio technologies mentioned above as well as other systemsand radio technologies. The description below, however, describes an LTEsystem for purposes of example, and LTE terminology is used in much ofthe description below, although the techniques are applicable beyond LTEapplications.

The detailed description set forth above in connection with the appendeddrawings describes exemplary embodiments and does not represent the onlyembodiments that may be implemented or that are within the scope of theclaims. The term “exemplary” used throughout this description means“serving as an example, instance, or illustration,” and not “preferred”or “advantageous over other embodiments.” The detailed descriptionincludes specific details for the purpose of providing an understandingof the described techniques. These techniques, however, may be practicedwithout these specific details. In some instances, well-known structuresand devices are shown in block diagram form in order to avoid obscuringthe concepts of the described embodiments.

Information and signals may be represented using any of a variety ofdifferent technologies and techniques. For example, data, instructions,commands, information, signals, bits, symbols, and chips that may bereferenced throughout the above description may be represented byvoltages, currents, electromagnetic waves, magnetic fields or particles,optical fields or particles, or any combination thereof.

The various illustrative blocks and modules described in connection withthe disclosure herein may be implemented or performed with ageneral-purpose processor, a digital signal processor (DSP), anapplication specific integrated circuit (ASIC), a field programmablegate array (FPGA) or other programmable logic device, discrete gate ortransistor logic, discrete hardware components, or any combinationthereof designed to perform the functions described herein. Ageneral-purpose processor may be a microprocessor, but in thealternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, multiple microprocessors, one or moremicroprocessors in conjunction with a DSP core, or any other suchconfiguration.

The functions described herein may be implemented in hardware, softwareexecuted by a processor, firmware, or any combination thereof. Ifimplemented in software executed by a processor, the functions may bestored on or transmitted over as one or more instructions or code on acomputer-readable medium. Other examples and implementations are withinthe scope and spirit of the disclosure and appended claims. For example,due to the nature of software, functions described above can beimplemented using software executed by a processor, hardware, firmware,hardwiring, or combinations of any of these. Features implementingfunctions may also be physically located at various positions, includingbeing distributed such that portions of functions are implemented atdifferent physical locations. Also, as used herein, including in theclaims, “or” as used in a list of items prefaced by “at least one of”indicates a disjunctive list such that, for example, a list of “at leastone of A, B, or C” means A or B or C or AB or AC or BC or ABC (i.e., Aand B and C).

Computer-readable media includes both computer storage media andcommunication media including any medium that facilitates transfer of acomputer program from one place to another. A storage medium may be anyavailable medium that can be accessed by a general purpose or specialpurpose computer. By way of example, and not limitation,computer-readable media can comprise RAM, ROM, EEPROM, CD-ROM or otheroptical disk storage, magnetic disk storage or other magnetic storagedevices, or any other medium that can be used to carry or store desiredprogram code means in the form of instructions or data structures andthat can be accessed by a general-purpose or special-purpose computer,or a general-purpose or special-purpose processor. Also, any connectionis properly termed a computer-readable medium. For example, if thesoftware is transmitted from a website, server, or other remote sourceusing a coaxial cable, fiber optic cable, twisted pair, digitalsubscriber line (DSL), or wireless technologies such as infrared, radio,and microwave, then the coaxial cable, fiber optic cable, twisted pair,DSL, or wireless technologies such as infrared, radio, and microwave areincluded in the definition of medium. Disk and disc, as used herein,include compact disc (CD), laser disc, optical disc, digital versatiledisc (DVD), floppy disk and blu-ray disc where disks usually reproducedata magnetically, while discs reproduce data optically with lasers.Combinations of the above are also included within the scope ofcomputer-readable media.

The previous description of the disclosure is provided to enable aperson skilled in the art to make or use the disclosure. Variousmodifications to the disclosure will be readily apparent to thoseskilled in the art, and the generic principles defined herein may beapplied to other variations without departing from the spirit or scopeof the disclosure. Throughout this disclosure the term “example” or“exemplary” indicates an example or instance and does not imply orrequire any preference for the noted example. Thus, the disclosure isnot to be limited to the examples and designs described herein but is tobe accorded the widest scope consistent with the principles and novelfeatures disclosed herein.

The invention claimed is:
 1. A method for configuring aZeroCorrelationZoneConfig (Ncs) parameter of a base station, comprising:determining by the base station a count of timing synchronizationfailures between a mobile device and the base station based at least inpart on non-receipt of a message at the base station, upon determiningthat the count of timing synchronization failures satisfies a threshold,dynamically configuring the Ncs parameter, and coordinating assignmentsof root sequences among a plurality of base stations, the root sequencesbeing used to generate physical random access channel (PRACH) preambles.2. The method of claim 1, further comprising detecting an occurrence ofa timing synchronization failure.
 3. The method of claim 2, whereindetecting the occurrence of the timing synchronization failurecomprises: receiving a first message comprising a preamble, generating apreamble identification (ID) for the received preamble, transmitting asecond message comprising the preamble ID, and upon transmission of thesecond message, detecting the non-receipt of the message.
 4. The methodof claim 2, wherein detecting the occurrence of the timingsynchronization failure comprises: receiving a first message comprisinga physical random access channel (PRACH) preamble, generating a preambleidentification (ID) for the received PRACH preamble, transmitting asecond message comprising the preamble ID, and upon transmission of thesecond message, detecting the non-receipt of the message in response tothe second message.
 5. The method of claim 4, further comprising:estimating a timing advanced value for the received PRACH preamble, thetiming advanced value indicating a first coverage area of the basestation, and maintaining a count of timing synchronization failures thatoccur in the first coverage area of the base station.
 6. The method ofclaim 1, further comprising: inserting information indicating anassignment of one or more root sequences assigned to the base stationinto a token, the one or more root sequences being used to generate aphysical random access channel (PRACH) preamble, and releasing the tokento a second base station.
 7. The method of claim 1, further comprising:receiving a token from a second base station, extracting, from thereceived token, information indicating an assignment of one or more rootsequences assigned to the second base station, the one or more rootsequences being used to generate a physical random access channel(PRACH) preamble, and adjusting an assignment of one or more rootsequences assigned to the base station based on the extractedinformation.
 8. The method of claim 7, wherein the token triggers thebase station to determine whether to adjust the Ncs parameter of thebase station.
 9. The method of claim 1, wherein coordinating theassignments of the root sequences comprises receiving instructions froma centralized server to determine whether to adjust one or more rootsequences currently assigned to the base station.
 10. The method ofclaim 1, wherein coordinating the assignments of the root sequencescomprises receiving a token from one of the plurality of base stations,the token triggering the base station to determine whether to adjust oneor more root sequences currently assigned to the base station.
 11. Themethod of claim 1, wherein upon determining that the count ofcommunication failures fails to satisfy the threshold, reducing the Ncsparameter.
 12. A base station for configuring aZeroCorrelationZoneConfig (Ncs) parameter, comprising: a processor; anda memory in electronic communication with the processor, the memoryembodying instructions, the instructions being executable by theprocessor to: determine by the base station a count of timingsynchronization failures between a mobile device and the base stationbased at least in part on non-receipt of a message at the base station,upon determining that the count of timing synchronization failuressatisfy a threshold, dynamically configuring the Ncs parameter, andcoordinate assignments of root sequences among a plurality of basestations, the root sequences being used to generate physical randomaccess channel (PRACH) preambles.
 13. The base station of claim 12,wherein the instructions are executable by the processor to detect anoccurrence of a timing synchronization failure.
 14. The base station ofclaim 13, wherein the instructions to detect the occurrence of thetiming synchronization failure are executable by the processor to:receive a first message comprising a preamble, generate a preambleidentification (ID) for the received preamble, transmit a second messagecomprising the preamble ID, and upon transmission of the second message,detect the non-receipt of the message.
 15. The base station of claim 13,wherein the instructions to detect the occurrence of the timingsynchronization failure are executable by the processor to: receive afirst message comprising a physical random access channel (PRACH)preamble, generate preamble identification (ID) for the received PRACHpreamble, transmit a second message comprising the preamble ID, and upontransmission of the second message, detect the non-receipt of themessage in response to the second message.
 16. The base station of claim15, wherein the instructions are executable by the processor to:estimate a timing value for the detected preamble, the timing valueindicating a particular coverage area of the base station, and maintaina count of detected PRACH preambles with the estimated timing value thatresult in a communication failure.
 17. The base station of claim 12,wherein the instructions are executable by the processor to: insertinformation indicating an assignment of one or more root sequencesassigned to the base station into a token, the one or more rootsequences being used to generate a physical random access channel(PRACH) preamble, and release the token to a second base station. 18.The base station of claim 12, wherein the instructions are executable bythe processor to: receive a token from a second base station, extract,from the received token, information indicating an assignment of one ormore root sequences assigned to the second base station, the one or moreroot sequences being used to generate a physical random access channel(PRACH) preamble, and adjust an assignment of one or more root sequencesassigned to the base station based on the extracted information.
 19. Thebase station of claim 18, wherein the token triggers the base station todetermine whether to adjust the Ncs parameter of the base station. 20.The base station of claim 12, wherein the instructions to coordinate theassignments of the root sequences are executable by the processor toreceive instructions from a centralized server to determine whether toadjust one or more root sequences currently assigned to the basestation.
 21. The base station of claim 12, wherein the instructions tocoordinate the assignments of the root sequences are executable by theprocessor to receive a token from one of the plurality of base stations,the token triggering the base station to determine whether to adjust oneor more root sequences currently assigned to the base station.
 22. Thebase station of claim 12, wherein upon determining that the count ofcommunication failures fails to exceed the threshold, the instructionsare executable by the processor to reduce the Ncs parameter.
 23. Anapparatus for configuring a ZeroCorrelationZoneConfig (Ncs) parameter,comprising: means for determining by the base station a count of timingsynchronization failures between a mobile device and a base stationbased at least in part on non-receipt of a message at the base station;means for dynamically configuring the Ncs parameter upon determiningthat the count of timing synchronization failures satisfies a threshold;and means for coordinating assignments of root sequences among aplurality of base stations, the root sequences being used to generatephysical random access channel (PRACH) preambles.
 24. The apparatus ofclaim 23, further comprising means for detecting an occurrence of atiming synchronization failure.
 25. The apparatus of claim 24, whereinthe means for detecting the occurrence of the timing synchronizationfailure comprises: means for receiving a first message comprising aphysical random access channel (PRACH) preamble; means for generatingpreamble identification (ID) for the received PRACH preamble; means fortransmitting a second message comprising the preamble ID; and upontransmission of the second message, means for detecting the non-receiptof the message in response to the second message.
 26. The apparatus ofclaim 25, further comprising: means for estimating a timing value forthe detected preamble, the timing value indicating a particular coveragearea of the base station; and means for maintaining a count of detectedPRACH preambles with the estimated timing value that result in acommunication failure.
 27. The apparatus of claim 23, furthercomprising: means for inserting information indicating an assignment ofone or more root sequences assigned to the base station into a token,the one or more root sequences being used to generate a physical randomaccess channel (PRACH) preamble; and means for releasing the token to asecond base station.
 28. The apparatus of claim 23, further comprising:means for receiving a token from a second base station; means forextracting, from the received token, information indicating anassignment of one or more root sequences assigned to the second basestation, the one or more root sequences being used to generate aphysical random access channel (PRACH) preamble; and means for adjustingan assignment of one or more root sequences assigned to the base stationbased on the extracted information.
 29. A computer program product forconfiguring a ZeroCorrelationZoneConfig (Ncs) parameter of a basestation, the computer program product comprising a non-transitorycomputer-readable medium storing instructions executable by a processorto: determine by the base station a count of timing synchronizationfailures between a mobile device and the base station based at least inpart on non-receipt of a message at the base station, upon determiningthat the count of timing synchronization failures satisfies a threshold,dynamically configuring the Ncs parameter, and coordinate assignments ofroot sequences among a plurality of base stations, the root sequencesbeing used to generate physical random access channel (PRACH) preambles.30. The computer program product of claim 29, wherein the instructionsare executable by the processor to detect an occurrence of a timingsynchronization failure.
 31. The computer program product of claim 30,wherein the instructions to detect an occurrence of a timingsynchronization failure are executable by the processor to: receive afirst message comprising a physical random access channel (PRACH)preamble, generate preamble identification (ID) for the received PRACHpreamble, transmit a second message comprising the preamble ID, and upontransmission of the second message, detect the non-receipt of themessage in response to the second message.
 32. The computer programproduct of claim 31, wherein the instructions are executable by theprocessor to: estimate a timing advanced value for the received PRACHpreamble, the timing advanced value indicating a first coverage area ofthe base station, and maintain a count of timing synchronizationfailures that occur in the first coverage area of the base station.